package main.java.servlet;

import main.java.pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns = {"/user"})
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User> users = new ArrayList<>();
        //jdbc操作数据库 查询

        // 1、加载驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 2、获取连接 (url username password)
            String url = "jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
            Connection connection = DriverManager.getConnection(url, "root", "zsy1960550415");
//            if (connection != null) {
//                System.out.println("连接成功");
//            }
            // 3、写sql
            String sql = "select * from user";

            // 4、预编译sql
            PreparedStatement preparedStatement = connection.prepareStatement(sql);

            // 5、有参数设置参数

            // 6、执行sql
            try (ResultSet resultSet = preparedStatement.executeQuery()) {

                // 7、遍历结果集
                while (resultSet.next()) {
                    User user = new User();
                    user.setId(resultSet.getInt(1));
                    user.setName(resultSet.getString(2));
                    user.setPassword(resultSet.getString(3));
                    //把对象添加到集合中
                    users.add(user);
                }

                // 8、关闭资源
            }
            preparedStatement.close();
            connection.close();

            //把集合中数据存储到作用域中
            req.setAttribute("users",users);
            //打开页面
            req.getRequestDispatcher("/user.jsp").forward(req,resp);


        } catch (ClassNotFoundException | SQLException e) {
            throw new RuntimeException(e);
        }


    }
}
